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            <h1 style="display: none">Javascript-重学Es之es6中的类和对象</h1>
            
            <div class="markdown-body">
              <h1 id="es6中的类和对象"><a href="#es6中的类和对象" class="headerlink" title="es6中的类和对象"></a>es6中的类和对象</h1><p><a href="http://quancundexiwang.wang/posts/62126/">es5中的类和对象</a></p>
<h2 id="class关键字"><a href="#class关键字" class="headerlink" title="class关键字"></a><code>class</code>关键字</h2><div class="code-wrapper"><pre class="line-numbers language-js" data-language="js"><code class="language-js"><span class="token keyword">class</span> <span class="token class-name">Person</span> <span class="token punctuation">&#123;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span> <span class="token comment">//constructor构造函数,new的时候执行</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> name<span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">const</span> p1 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Person</span><span class="token punctuation">(</span><span class="token string">'ChangHao'</span><span class="token punctuation">,</span> <span class="token number">22</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>p1<span class="token punctuation">)</span> <span class="token comment">//Person&#123;name: "ChangHao", age: 22&#125;</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div>
<h2 id="class定义类的methods"><a href="#class定义类的methods" class="headerlink" title="class定义类的methods"></a><code>class</code>定义类的<code>methods</code></h2><blockquote>
<p>es5中给类定义类的方法,都是在定义完类后再把方法定义到类的原型上 `Person.prototype.mehod = function(){…},然鹅当我们使用<code>class</code>关键字，就很简单的把方法定义在类内部就好啦！</p>
</blockquote>
<div class="code-wrapper"><pre class="line-numbers language-js" data-language="js"><code class="language-js"><span class="token keyword">class</span> <span class="token class-name">Person</span> <span class="token punctuation">&#123;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span> <span class="token comment">//constructor构造函数,new的时候执行</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> name<span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token function">showName</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>name<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">const</span> p1 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Person</span><span class="token punctuation">(</span><span class="token string">'ChangHao'</span><span class="token punctuation">,</span> <span class="token number">22</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>p1<span class="token punctuation">.</span><span class="token function">showName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">//ChangHao</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div>
<h2 id="static-定义类的静态属性和方法"><a href="#static-定义类的静态属性和方法" class="headerlink" title="static 定义类的静态属性和方法"></a><code>static</code> 定义类的静态属性和方法</h2><div class="code-wrapper"><pre class="line-numbers language-javascript" data-language="javascript"><code class="language-javascript"><span class="token keyword">class</span> <span class="token class-name">Person</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">static</span> count <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>

    <span class="token keyword">static</span> <span class="token function">showCount</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> Person<span class="token punctuation">.</span>count<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>

    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span> <span class="token comment">//constructor构造函数,new的时候执行</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> name<span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age<span class="token punctuation">;</span>
        Person<span class="token punctuation">.</span>count<span class="token operator">++</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>

    <span class="token function">showName</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>name<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">const</span> p1 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Person</span><span class="token punctuation">(</span><span class="token string">'ChangHao'</span><span class="token punctuation">,</span> <span class="token number">22</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">const</span> p2 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Person</span><span class="token punctuation">(</span><span class="token string">'ZhiHong'</span><span class="token punctuation">,</span> <span class="token number">22</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>Person<span class="token punctuation">.</span>count<span class="token punctuation">)</span><span class="token comment">//2</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>Person<span class="token punctuation">.</span><span class="token function">showCount</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token comment">//2</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div>
<h2 id="es6类的继承-lt-extends-super-gt-关键字"><a href="#es6类的继承-lt-extends-super-gt-关键字" class="headerlink" title="es6类的继承&lt; extends , super&gt;关键字"></a>es6类的继承&lt; <code>extends</code> , <code>super</code>&gt;关键字</h2><h3 id="1-简单介绍"><a href="#1-简单介绍" class="headerlink" title="1.简单介绍"></a>1.简单介绍</h3><blockquote>
<p>继续拿学习es5中的常氏家族，做类的继承的例子</p>
</blockquote>
<div class="code-wrapper"><pre class="line-numbers language-js" data-language="js"><code class="language-js"><span class="token keyword">class</span> <span class="token class-name">ChangFamily</span> <span class="token punctuation">&#123;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> <span class="token template-string"><span class="token template-punctuation string">`</span><span class="token string">常</span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">$&#123;</span>name<span class="token interpolation-punctuation punctuation">&#125;</span></span><span class="token template-punctuation string">`</span></span><span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age<span class="token operator">+</span><span class="token number">2</span><span class="token punctuation">;</span> <span class="token comment">//老常家虚岁两岁</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">class</span> <span class="token class-name">childFromChang</span> <span class="token keyword">extends</span> <span class="token class-name">ChangFamily</span> <span class="token punctuation">&#123;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age<span class="token punctuation">,</span> work</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">super</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> age<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">//super调用父类的构造函数。</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>work <span class="token operator">=</span> work<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>
<span class="token keyword">const</span> firstChildFromChang <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">childFromChang</span><span class="token punctuation">(</span><span class="token string">'昊'</span><span class="token punctuation">,</span><span class="token number">23</span><span class="token punctuation">,</span><span class="token string">'front_end_dev'</span><span class="token punctuation">)</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>firstChildFromChang<span class="token punctuation">)</span> 
<span class="token comment">//childFromChang &#123;name: "常昊", age: 25, work: "front_end_dev"&#125;</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div>
<p><code>extends</code> 后面跟的是当前定义的类要继承的<code>超类</code>，也可以通俗的理解为<code>父类</code>，可以通过<code>super</code>关键字调用父类的<code>构造函数</code>。</p>
<h3 id="2-子类访问父类的静态属性，静态方法和实例方法"><a href="#2-子类访问父类的静态属性，静态方法和实例方法" class="headerlink" title="2.子类访问父类的静态属性，静态方法和实例方法"></a>2.子类访问父类的静态属性，静态方法和实例方法</h3><div class="code-wrapper"><pre class="line-numbers language-js" data-language="js"><code class="language-js"><span class="token keyword">class</span> <span class="token class-name">ChangFamily</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">static</span> childCount <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>

    <span class="token keyword">static</span> <span class="token function">countChildNum</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> ChangFamily<span class="token punctuation">.</span>childCount<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>

    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> <span class="token template-string"><span class="token template-punctuation string">`</span><span class="token string">常</span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">$&#123;</span>name<span class="token interpolation-punctuation punctuation">&#125;</span></span><span class="token template-punctuation string">`</span></span><span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age <span class="token operator">+</span> <span class="token number">2</span><span class="token punctuation">;</span> <span class="token comment">//老常家虚岁两岁</span>
        ChangFamily<span class="token punctuation">.</span>childCount<span class="token operator">++</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>

    <span class="token function">showSelf</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> <span class="token template-string"><span class="token template-punctuation string">`</span><span class="token string">我是</span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">$&#123;</span><span class="token keyword">this</span><span class="token punctuation">.</span>name<span class="token interpolation-punctuation punctuation">&#125;</span></span><span class="token string">,我今年</span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">$&#123;</span><span class="token keyword">this</span><span class="token punctuation">.</span>age<span class="token interpolation-punctuation punctuation">&#125;</span></span><span class="token string">岁了</span><span class="token template-punctuation string">`</span></span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">class</span> <span class="token class-name">childFromChang</span> <span class="token keyword">extends</span> <span class="token class-name">ChangFamily</span> <span class="token punctuation">&#123;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age<span class="token punctuation">,</span> work</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">super</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> age<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//super调用父类的构造函数。</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>work <span class="token operator">=</span> work<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">const</span> firstChildFromChang <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">childFromChang</span><span class="token punctuation">(</span><span class="token string">'昊'</span><span class="token punctuation">,</span> <span class="token number">23</span><span class="token punctuation">,</span> <span class="token string">'front_end_dev'</span><span class="token punctuation">)</span>

console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>childFromChang<span class="token punctuation">.</span>childCount<span class="token punctuation">)</span> <span class="token comment">//1 子类访问父类的静态属性</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>childFromChang<span class="token punctuation">.</span><span class="token function">countChildNum</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">//1 子类调用父类的静态方法</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>firstChildFromChang<span class="token punctuation">.</span><span class="token function">showSelf</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">//我是常昊,我今年25岁了子类实例对象调用父类的方法</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div>


<h2 id="用其他姿势来定义属性-lt-get取值-set赋值-gt"><a href="#用其他姿势来定义属性-lt-get取值-set赋值-gt" class="headerlink" title="用其他姿势来定义属性&lt;get取值,set赋值&gt;"></a>用其他姿势来定义属性&lt;<code>get取值</code>,<code>set赋值</code>&gt;</h2><blockquote>
<p>为什么有了构造器初始化定义对象的属性，而且后面也可以赋值对象的属性，来修改对象的属性，为什么还要多一个<code>get,set</code>来操作对象的属性，增加学习成本呢？</p>
</blockquote>
<blockquote>
<p>其实使用<code>get,set</code>,可以更好的对属性进行控制，满足更强大的业务场景。</p>
</blockquote>
<blockquote>
<p>比如我们可以限制🚫一些对象属性的定义，比如<code>gender</code>性别只能传男0或女1，那你又说了，构造器中也能实现啊！但是当你很多属性都要做限制的话，你的构造器就会显得很不优雅，你可以做，但是我不建议。</p>
</blockquote>
<div class="code-wrapper"><pre class="line-numbers language-js" data-language="js"><code class="language-js"><span class="token keyword">class</span> <span class="token class-name">ChangFamily</span> <span class="token punctuation">&#123;</span>
	  _gender <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>name <span class="token operator">=</span> <span class="token template-string"><span class="token template-punctuation string">`</span><span class="token string">常</span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">$&#123;</span>name<span class="token interpolation-punctuation punctuation">&#125;</span></span><span class="token template-punctuation string">`</span></span><span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>age <span class="token operator">=</span> age <span class="token operator">+</span> <span class="token number">2</span><span class="token punctuation">;</span> <span class="token comment">//老常家虚岁两岁</span>
        ChangFamily<span class="token punctuation">.</span>childCount<span class="token operator">++</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token keyword">set</span> <span class="token function">gender</span><span class="token punctuation">(</span><span class="token parameter">val</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>val <span class="token operator">==</span> <span class="token number">1</span> <span class="token operator">||</span> val <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
            <span class="token keyword">this</span><span class="token punctuation">.</span>_gender <span class="token operator">=</span> val<span class="token punctuation">;</span>
        <span class="token punctuation">&#125;</span> <span class="token keyword">else</span> <span class="token punctuation">&#123;</span>
            <span class="token keyword">new</span> <span class="token class-name">Error</span><span class="token punctuation">(</span><span class="token string">'性别只能是 男0或女1'</span><span class="token punctuation">)</span>
        <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token keyword">get</span> <span class="token function">gender</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>_gender<span class="token operator">==</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
            <span class="token keyword">return</span> <span class="token string">'male 男人'</span><span class="token punctuation">;</span>
        <span class="token punctuation">&#125;</span><span class="token keyword">else</span> <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>_gender<span class="token operator">==</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
            <span class="token keyword">return</span> <span class="token string">'female 女人'</span><span class="token punctuation">;</span>
        <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">class</span> <span class="token class-name">childFromChang</span> <span class="token keyword">extends</span> <span class="token class-name">ChangFamily</span> <span class="token punctuation">&#123;</span>
    <span class="token function">constructor</span><span class="token punctuation">(</span><span class="token parameter">name<span class="token punctuation">,</span> age<span class="token punctuation">,</span> work</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token keyword">super</span><span class="token punctuation">(</span>name<span class="token punctuation">,</span> age<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>work <span class="token operator">=</span> work<span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">const</span> firstChildFromChang <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ChangFamily</span><span class="token punctuation">(</span><span class="token string">'昊'</span><span class="token punctuation">,</span> <span class="token number">23</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
firstChildFromChang<span class="token punctuation">.</span>gender <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>firstChildFromChang<span class="token punctuation">.</span>gender<span class="token punctuation">)</span> <span class="token comment">//male 男人</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div>
<p><span style='color:red'>父类的<code>get&amp;set</code>也会被子类继承</span></p>
<div class="code-wrapper"><pre class="line-numbers language-js" data-language="js"><code class="language-js"><span class="token keyword">const</span> firstChildFromChang <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">childFromChang</span><span class="token punctuation">(</span><span class="token string">'小x'</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span>
firstChildFromChang<span class="token punctuation">.</span>gender <span class="token operator">=</span> <span class="token number">1</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>firstChildFromChang<span class="token punctuation">.</span>gender<span class="token punctuation">)</span> <span class="token comment">//female 女人</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span></span></code></pre></div>
<p class='note note-warining'>`class` 只是es5定义类的语法糖！es5中的一些用法在这里也是可以用的， </p>



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